This invention relates to fuel cell systems and, in particular, to fuel cell systems in which cooling of the fuel cells with process gas is employed.
In U.S. Pat. No. 4,192,906, a fuel cell system is disclosed wherein the fuel cell includes first and second electrolyte communicative passages for carrying first and second (i.e., oxidant and fuel) process gases to first and second electrodes of the cell. The cell also includes a third electrolyte-isolated passage in thermal communication with a heat generating surface of the cell for carrying a cooling gas through the cell. A first process gas is supplied to the first electrolyte-communicative passage and is split between that passage and the electrolyte-isolated passage by feeding such process gas from its supply to an input manifold common to both sets of passages. In this way, the first process gas also serves as the cooling gas. This patent also teaches that the output gas from the electrolyte-isolated passage either alone or after mixing with the output gas of the first electrolyte-communicative passage, can be fed to the common input manifold for recirculation.
While the fuel cell arrangement of the '906 patent results in successful cooling, it may cause dilution of the first process gas passing through the first electrolyte-communicative passage. This, in turn, reduces the performance of the fuel cell.
U.S. Pat. Nos. 4,276,355 and 4,342,816 disclose a further fuel cell system wherein first and second electrolyte-communicative passages carry process gas and a third electrolyte-isolated passage carries cooling gas through the cell and independent manifolds feed the respective passages. While this type of arrangement can be used to avoid dilution effects, three independent gas streams (i.e., first and second process gas streams and a cooling gas stream) are contemplated.
It is therefore an object of the present invention to provide a fuel cell sytem which offers certain improvements over the above-described arrangements.
It is a further object of the present invention to provide a fuel cell system in which cooling can be achieved with independent manifolds, but without the necessity for three independent gas streams.
It is a further object of the present invention to provide a fuel cell system of the last mentioned type in which cooling can be further realized while inhibiting dilution effects.